Fix repository create, list, and update test mocking to use withSdk pattern

Convert fetch-create-repo, fetch-list-repos, and fetch-update-repo tests from
setupSdk + handleApiCall mocking pattern to withSdk pattern to match actual
implementation. Add beforeEach hooks for proper mock cleanup between tests.

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: jdalton